Graft copolymers, because of their structural features, are effectively used as functional polymers such as functionalizing agents for polymers, surfacing agents, compatibilizers for polymer blends, and surfactants for polymer/filler compound materials. Polyolefin graft copolymers are typically prepared by grafting of vinyl monomers to polyolefins via free radicals; however, the grafting efficiency is basically low.
A Ziegler-Natta catalyst and a more recent metallocene catalyst are famous as the coordination polymerization catalysts for olefins. Since these early transition metal-based catalysts have low tolerance to polar compounds in particular, processes such as copolymerization of olefins with monomers having protected functional groups or functional group precursor monomers, formation of functional groups, and then graft polymerization initiating from functional groups or coupling with other reactive polymer, are necessary in order to form various graft copolymers. Here the term “tolerance” means that polar compounds do not readily coordinate with complexes or catalyst activated species and, even if they did, they do not readily become inert. It also means that catalyst do not readily react with polar compounds or do not readily decompose.
Another effective method for making graft copolymers in the presence of olefin coordination polymerization catalysts is graft polymerization of olefins and macromonomers (also referred to as macromers). Japanese Examined Patent Application Publication No. 54-10996 discloses a method for preparing a copolymer of α-olefin and an α-olefin-terminated macromonomer (e.g., polystyrene; use of polyisobutylene is also disclosed although this does not relate to the anionic polymerization) prepared by anionic polymerization in the presence of a Ziegler catalyst. However, since bulky monomers rarely coordinate, the grafting efficiency is normally low. Use of early transition metal complexes, which have low tolerance to polar materials, is particularly disadvantageous in conducting graft copolymerization of (meth)acryl macromonomer or graft copolymerization in air, in the presence of moisture, in the presence of wet materials, in the presence of polar compounds, or in water.
As illustrated in the reviews of Chem. Rev. 2000, 100, 1169, Yuki Gosei Kagaku Kyokaishi (Journal of Synthetic Organic Chemistry, Japan), 2000, 58, 293, and Angew. Chem. Int. Ed. 2002, 41, 544; and in WO 97/17380, WO 97/48740, Chem. Commun. 200, 301, Macromol. Symp. 2000, 150, 53, Macromolecules, 2001, 34, 1165, and Macromolecules, 2001, 34, 2022, coordination polymerization catalysts based on late transition metal complexes are now drawing much attention since these catalysts have high tolerance to polar compounds such as polar monomer (e.g., polar vinyl monomers such as (meth)acrylate) and polar solvents (e.g., tetrahydrofuran, ethers, acetones, ethy acetate, and water). Macromol. Chem. Phys. 2000, 201, 1823 reports graft copolymerization for ethyelene and a polystyrene macromonomer (prepared from polystyrene living anions and allyl bromide) using a palladium complex containing an α-diimine ligand. However, the copolymerization was conducted in argon atmosphere and nearly all ingredients were dry ingredients. No report has been present regarding graft copolymerization of olefins and (meth)acryl macromonomers and graft copolymerization in air, in the presence of moisture, in the presence of wet materials, in the presence of polar compounds, or in water.
Japanese Unexamined Patent Application Publication No. 10-316711 also discloses a polyolefin-polyisobutylene graft copolymer. Since this technology uses a C2-symmetrical crosslink metallocence catalyst, the resulting polyolefin from α-olefin having at least three carbon atoms has stereoregularity. [It was reported that since bulky monomers do not readily coordinate to nonsymmetrical and noncrosslink metallocence catalysts, e.g., bis(cyclopentadienyl)zirconocene, ethylene and propylene macromonomers (synthesized by selective β-methy elimination in propylene polymerization with bis(pentamethylcyclopentadienyl)zirconocene) do not copolymerize with each other (Macromol. Symp. Phys. 1995, 97, 161).] However, no report is present regarding polypropylene (PP)/polyisobutylene (PIB) graft copolymers, which has no stereoregularity (atactic), i.e., is amorphous, and has a high grafting efficiency or regarding methods for making such copolymers. As is described above, since the tolerance to polar compounds is low, the graft copolymerization is difficult in air, in the presence of moisture, in the presence of wet material, in the presence of polar compounds, or in water.